The invention relates to a device for performing measurements in a space by means of a chip, especially for measuring the static or dynamic pressure in said space.
Such devices are for instance used in internal combustion engines and diesel engines for measuring the pressure in for instance the internal combustion chamber, the injection conduits, etc.
Such devices can be applied furthermore in the chemical industry where in the process often gases or fluids with a predetermined steady or variable temperature and/or pressure have to be used and whereby the instantaneous value of the temperature and/or pressure forms one of the control parameters of the respective process.
Furthermore such a device can be used for monitoring the temperature and/or pressure in supply tanks in which fluids or gases are stored and maintained under pressure.
It is known to use semiconductor components in these devices for performing the measurements. Thereby the semiconductor component is mounted onto a substrate and is through bonding wires connected to connecting pads or directly to a pattern of conductors. The signals, generated within the semiconductor component under the influence of the measured parameter, are guided to the external surroundings through these bonding wires. Bonding wires have the disadvantage that they are very thin and are therefore very liable to breakage. Furthermore, applying these bonding wires requires the use of specific bonding apparatuses.
In recent times, semiconductor components use so-called flip-chip mounting. No bonding wires are used for mounting these semiconductor components; instead the semiconductor components have connecting surfaces by means of which the components can be directly connected onto a pattern of conductors, for instance by means of soldering. The carrier, onto which the component has to be mounted, comprises a number of connecting surfaces in a corresponding pattern. To mount the semiconductor components on the connecting surfaces of the carrier, small drops of fluid solder are applied and thereafter the semiconductor component is positioned and soldered. More information about this flip-chip method is, for instance, available in U.S. Pat. No. 5,346,857 and U.S. Pat. No. 5,284,796.
If one likes to use these semiconductor components which are destined for flip-chip mounting, especially for performing measurements in environments in which besides the parameter to be measured furthermore strong temperature changes may appear, such as for instance is the case in internal combustion engines and in many chemical processes, then problems will arise in relation to the mounting of the semiconductor component on the carrier. In general, a pressure sensitive chip comprises a membrane, which forms part of the actual pressure measuring chip. With the known semiconductor components destined for bonding wire mounting, this membrane is in the operating situation positioned at the side which is not adjacent to the underlying carrier. An example thereof are described in U.S. Pat. No. 4,763,098. With components for flip-chip mounting, however, this membrane is often at the side which is adjacent to the carrier. Because the solder droplets used during flip chip mounting are very small it is certainly not inconceivable that the distance between the surface of the carrier element and the membrane, if any at all, becomes to small to assure that the pressure at the membrane surface allways equals the pressure to be measured.
An object of the invention is now to indicate in which manner these problems can be eliminated and in which manner it is therefore possible to assure a correct pressure measurement.
In agreement with said object the invention now provides a device for performing measurements in a space by means of a chip, especially for measuring the static or dynamic pressure in said space, comprising:
a semiconductor component suitable for the measuring purposes, which component during operation is positioned in said space and has connecting pads for flip-chip mounting,
a support element comprising a flat surface carrying a pattern of conductors onto which said semiconductor component can be attached,
characterized in that spacer elements are installed between the pattern of conductors on the support element and the connecting pads of the semiconductor component such that after performing the flip chip mounting process there is a space between the semiconductor component and said surface of the support element in wich space the pressure equals the pressure to be measured.